CoCrW Alloy Material Performance, Characteristic and Application

Author： 超級管理員 Time：2023-05-03 13:59:54 Read：1054

Kunshan Materevo Technology Co., Ltd. has cooperated with domestic universities for many years in research and development of cobalt chromium tungsten (CoCrW) alloy ball products and conventional alloy structural components products, and has made breakthroughs in geological exploration, polar drilling, mineral exploration, coal machinery, oil drilling, and marine deep drilling. We hope to collaborate in the field of cobalt chromium tungsten (CoCrW) alloy products and jointly develop excellent products to meet future front-end industrial applications. For this purpose, our company has specially collected some professional technical materials for your reference.

Cobalt chromium tungsten (CoCrW) alloy is a high-temperature alloy based on cobalt (Co), mainly in two combination forms: (a) tungsten (W) family composed of Co cr W c. (b) Molybdenum (Mo) groups containing Co Cr Mo C.

Cobalt chromium tungsten (CoCrW) alloy has excellent corrosion resistance, oxidation resistance, wear resistance, heat resistance, and low magnetic permeability. Components made of cobalt chromium tungsten alloy work well in highly corrosive environments and maintain these superior properties at high temperatures. Components made of cobalt chromium tungsten alloy are widely used in petroleum and natural gas vehicles, nuclear power, paper and pulp, chemistry and petrochemicals, refineries, automobiles, aerospace, and aviation industries. Due to its non magnetic, anti-corrosion, and non reactivity to human body fluids. Cobalt chromium tungsten alloy is used in medical surgery, surgical tools, dental and bone implants and substitutes, heart valves, and pacemakers.

Cobalt chromium tungsten (CoCrW) alloy has a hardness range of 32 to 55 HRC and belongs to brittle materials, but its Young's modulus is relatively low. Due to the high hardness, high density but uneven, molecular structure and low thermal conductivity of cobalt chromium tungsten alloy, it is extremely difficult to process cobalt chromium tungsten alloy parts. Cobalt chromium tungsten alloy is classified as difficult to machine materials like titanium alloy. Chromium nickel iron alloy, composite materials, and stainless steel are typically produced on a steel substrate using a deposition method for machine parts made of cobalt chromium tungsten alloy, rather than using expensive solid cobalt chromium tungsten alloy rods. The rough surface of deposited cobalt chromium tungsten (CoCrW) alloy is achieved through grinding, rather than other economic processing processes, which are both expensive and time-consuming, making tungsten chromium cobalt alloy products very expensive.

Cobalt chromium tungsten (CoCrW) alloy has had an inspiring history from the beginning. Elwood P. Haynes was one of the two earliest inventors of the horseless carriage in human history, and he developed a lot of cobalt in his laboratory. Based on metal alloys, he named these alloys "cobalt chromium tungsten alloys" in the 20th century for the production of various key components of internal combustion engines, as well as more robust lathe tools for machining carriage free components. The name Haines comes from the Latin word "Stella", which means "stars" because they have the same luster as stars. Compared to other metals and metal alloys, these alloys have a very high hardness; Initially, Haines developed nickel chromium (Ni Cr) alloys and cobalt chromium (Co Cr) alloys, and obtained patents for these two high-temperature alloys in 1907. Based on his subsequent research, Haines produced two new sets of cobalt based allovs with the addition of tungsten (W) and molybdenum (Mo). He added these two new allovs, named "Stellites", and obtained a patent in 1912. Haines developed tungsten chromium cobalt alloy in the laboratory for the production of new corrosion-resistant and heat-resistant metals for automotive components, dental instruments, and surgical tools. Sharp tools, tableware. Metal processing tools, and many other applications that require anti-corrosion, high wear resistance, high hardness, and longer heat resistance. Haines obtained another patent in 1913 because he developed a cobalt chromium molybdenum tungsten carbon composite high-temperature alloy (Co Cr Mo W-C), known as Havnis alloy 6E.

Nowadays, many cobalt chromium tungsten alloys are made by mixing different amounts/proportions of cobalt, including chromium, molybdenum, tungsten, titanium, nickel, iron, aluminum, carbon, boron, manganese, phosphorus, silicon, and sulfur. Due to its low magnetic permeability and excellent anti-corrosion performance, cobalt chromium tungsten alloy is very suitable for medical surgery, dental implants, bone replacement, artificial heart valves, and pacemakers. Due to its high hardness and good ductility, dense molecular structure, regular hard carbide structure, low thermal conductivity, low tendency of plastic deformation resistance, CoCrW alloy and other cobalt based alloys, such as titanium alloy, are classified as difficult to process materials with poor processing performance. The machinability of materials is determined by surface roughness to obtain quality and surface integrity, tool life, cutting zone heating, difficulty in chip formation, material removal rate (MRR) and power consumption, and machine dynamics, among other parameters involved in metal processing. Difficult to machine materials refer to the materials that cause excessive tool wear. The cutting force is too large, the heat generated is high, the chip formation is difficult, and the surface finish is difficult to machine in the processing operation. An important phenomenon in material processing is the excessive heat generated in the cutting zone, which leads to a very high temperature increase in the primary and secondary cutting zones. The shear zone and built-up edges (BUE) also lead to phase transformation on the machined surface, leading to premature tool damage.

Due to the poor cutting performance of cobalt alloys, most components made from these alloys are produced through precision casting: powder metallurgy and sintering. The use of grinding and unconventional machining techniques (such as electric discharge machining, LBM, etc.) has led to low productivity and high manufacturing costs for cobalt alloy components, especially for medical implants such as hip and dental implants.

Cobalt is a tough silver gray low permeability metal with a light blue hue. Cobalt appears in the CPH structure below 4210 ℃, and in the FCC lattice structure above this temperature. Cobalt has a high radioactive Curie point/temperature (1121 ° C), and due to its ductility, it has high damping properties. These characteristics make cobalt a useful component/inclusion in vibration and high-temperature alloys. Cobalt exists in 26 isotopes from Co-50 to Co-75. Co-59 is the only stable isotope among them. The magnetic permeability of cobalt is about 2/3 of that of iron. Make cobalt alloy a non magnetic biomaterial second only to titanium alloy. The density of cobalt is 8.90 grams per cubic centimeter, and the atomic mass is 58.9332 amu. The melting point of cobalt is 1495 ° C. All of these characteristics are beneficial for improving the performance of Co allovs. Adding cobalt to metal tool materials helps to reduce the friction coefficient in the cutting zone (interaction between tool and workpiece material) and helps to maintain red hardness. Cobalt based alloys are suitable for chemical environments that require higher corrosion resistance, wear resistance, high strength at high temperatures, and good corrosion resistance. Cobalt chromium tungsten alloy is also suitable for the fields requiring high creep resistance, structural stability, thermal creep resistance and thermal corrosion resistance. As mentioned earlier, there are currently two main combinations of cobalt chromium tungsten alloys. Co Cr W-C combination containing W: such as cobalt chromium tungsten alloy 6 Cobalt chromium tungsten alloy 12. Cobalt chromium tungsten ore 1 and cobalt chromium tungsten ore 190, as well as Co Cr Mo C combinations containing Mo, such as cobalt chromium tungsten ore 706. Cobalt chromium tungsten alloy 712. Cobalt chromium tungsten alloy 701 and Cobalt chromium tungsten alloy 790.

The high chromium (Cr) content provides cobalt chromium tungsten alloy with high corrosion resistance, wear resistance, and good magnetic properties at high temperatures. Chromium, as a carbide forming agent, is the most important strengthening element in the alloy matrix. Chromium also provides excellent corrosion resistance and oxidation resistance alloys. Tungsten (W) and molybdenum (Mo) are the main elements in tungsten chromium cobalt alloys, which can improve the strength of the alloy matrix. Molybdenum helps to increase hardness and forms hard and stable carbides in alloys. Molybdenum itself has the sixth highest melting point (2623 ° C) in known materials. Tungsten (W), as an alloying element, has sufficient toughness and hardness. High density, high red hardness. Carbon provides alloys with lower conductivity but highest thermal conductivity. The carbides in cobalt chromium tungsten alloy provide high hardness and red hardness for the alloy.

The formation of hard carbides in steel crystal alloys provides sliding wear and wear resistance, while chromium carbide (Cr-C) matrix provides wear resistance, cavitation and corrosion. Cobalt chromium tungsten alloy has excellent metal to metal wear resistance.

Table 1 below shows the chemical composition of different grades of cobalt chromium tungsten alloys, while Table 2 shows the mechanical properties of some available cobalt chromium tungsten alloys.

As shown in Table 2, the elongation coefficients of cobalt chromium tungsten alloys 6 and 12 are very low, while cobalt chromium tungsten alloys 6B and 21 are high enough to adapt to various applications. Therefore, cobalt chromium tungsten alloys 6B and 21 have relatively low hardness, high elongation, and high ductility. Make them suitable for purposes that require lower brittleness, and these cobalt chromium tungsten alloys are used as excellent biomaterials. Hard cobalt chromium tungsten alloys, such as cobalt chromium tungsten alloy 6, are used for hard faced mud valves in alumina refinery with very high wear and corrosion rates. These valves require precise machining to provide better functional surface matching to prevent fluid leakage and prevent excessive wear and corrosion of the valve. Better surface finish can also reduce the occurrence of corrosion and Corrosion fatigue cracks. The excellent performance of unutumau cobalt alloy is attributed to the crystalline properties of cobalt, the solid solution strengthening effect of chromium (Cr) and molybdenum (Mo), the formation of extremely hard carbides, and the corrosion and wear resistance of chromium. Tungsten (W) provides high density in cobalt alloys, creating high hardness and red hardness, with great ductility and high heat resistance. The molybdenum in cobalt alloy promotes the hard and stable carbides in the alloy. As mentioned earlier, the melting point of molybdenum itself ranks sixth among known metals (2.623 ° C)

The industrial application of cobalt chromium tungsten alloy In the engineering industry, the reason for using cobalt chromium tungsten alloy is to provide a corrosion-resistant and wear-resistant surface, which will help resist the wear and corrosion of mechanical components. However, wear-resistant materials have the characteristic of uniform distribution. The dense carbide matrix is naturally difficult to machine due to its high carbide content. In some cases, the distribution of hard alloys is uneven. The lower thermal conductivity and higher hardness result in poor cutting performance of these materials.

Cobalt based alloys are sometimes non magnetic materials but have high strength. These alloys are known for their high wear, corrosion resistance, and heat resistance, and are materials with high hardness but sufficient ductility. These alloys can maintain their strength well even at high temperatures for a long period of time, and perform well in corrosive and acidic environments. As mentioned earlier, cobalt based alloys exhibit excellent degradation resistance in body fluid environments, which has enabled their successful application in internal medicine surgeries and surgical implants. Several medical tests have confirmed that cobalt based alloys have biocompatibility and are suitable for use as surgical implants and bone replacements.

According to its conventional application, it can be divided into the following types:

L wear-resistant alloy,

High temperature alloy,

Corrosion resistant alloy.

Cobalt chromium tungsten alloy (Stellite 6B) and tungsten chromium cobalt alloy (Stellite 6K) are wear-resistant alloys with a high proportion (about 30%) of Cr and about 65% Co. High proportion Cr is the main carbide forming agent in the alloy solidification process, with high strength. The excellent wear resistance of these alloys is attributed to the formation of the most uniform cobalt rich matrix of carbide grains. Cobalt chromium tungsten alloy 6, due to its excellent wear resistance and toughness, has been widely used in the manufacturing of cutting bits for deep drilling equipment such as mining and rock. Crushing rollers, cement and steel equipment, conveying systems, steam turbine anti-corrosion covers, semi casings and bushings that cannot be lubricated or effectively lubricated. Cobalt chromium tungsten alloy 6K. There is no molybdenum (Mo) in its composition, only 30% of Cr, and it has a high hardness (47 HRC). Is it highly suitable for producing organic and plant materials used for cutting soft materials, such as tobacco.

Another alloy, Stellite 3, has a tungsten (W) three times that of Stellite 6, 6B, and 6K, and does not contain molybdenum. It is not recommended to use Stellite 6, 6B, and 6K in corrosive environments. However, due to the high carbon (C) content, the volume fraction of carbides increases, and the wear resistance of Stella 3 is 3-4 times that of Stella 6 and twice that of Stella 12. Stellite 3 has higher red hardness and corrosion resistance, and is worn like all Stellite alloys. Therefore, it is recommended to use Stellite 3 to manufacture bearing balls and needles, sleeves and bushings, valve seat inserts in non corrosive environments, surgical scissors type inserts, burner nozzles, steel mill guide rollers and sealing rollers.

Stellite is a very useful and popular representative of cobalt based alloy group. As mentioned above, due to the above excellent mechanical properties, Stellite has been applied in many industries, such as oil and gas, automobile, aerospace, pulp and paper, food processing, wood and timber, nuclear industry and medical surgery for production. Surgical tools and replacement of human bones/components. The application summary of Stellite in various fields is as follows.

Oil, gas, and mining industries

Most mechanical components in the oil, mining, and natural gas industries are subject to corrosion, wear, high pressure, wear, and high temperatures. Cobalt based alloys, such as Stellite 6, 12, 21, and 6B, provide excellent wear and corrosion resistance, thereby extending component life. According to the wear-resistant company Tai Li, it is said that oil, natural gas, and mining exploration equipment manufacturers as well as mineral explorers in this field [9]. The commonly used machine components and gas industries made of Stellite 6, 12, 21, and 6B in engine oil are as follows:

MWD (measurement while drilling) and LWD (logging while drilling) internal wear tools, such as rotors, stators, impellers, stabilizers, corrosion inserts, landing, wear and turbine sleeves, fishing heads;

Filter screen;

Kelly valve trim;

Cage;

Sucker rod coupling;

Annular blowout preventer;

Ball and seat;

Underground safety valves (baffles, darts);

Drill bit.

As shown in Tables 1 and 2, tungsten chromium cobalt alloys 6, 12, and 6B are alloys rich in tungsten (W), with very low elongation (metal close to 1%) and high hardness in the range of 40-50 HRC. Tungsten chromium cobalt alloy 6 and tungsten chromium cobalt alloy 12 contain a high proportion of chromium (Cr), which gives them high wear and corrosion resistance and improves hardness. All of these characteristics make mechanical components highly survivable in onshore and offshore oil and gas factories as well as deep-sea drilling sites.

Wear and corrosion issues are said to be major issues in the refining industry. Cobalt chromium tungsten alloy can solve this problem. Extend service life, reduce unplanned downtime, and reduce maintenance costs. The main products of Stellite 6 and 12 used in refineries and petrochemical industry include various nozzles, thermowells, valves, valve seats, valve sliders and balls, valve plugs, valve trims, fluid catalytic cracking unit components and pump components. Cast tungsten chromium cobalt alloy pump casings and impellers have the longest service life, and nozzles of various sizes and shapes are used in oil refining and petrochemical processing plants to inject and introduce high-pressure steam, compressed air, hydrocarbons, and other chemicals. The air grid nozzles, reactor feed and other feed nozzles, regeneration chamber air grid nozzles, stripping nozzles, and orifice chamber nozzles are all made of cobalt chromium tungsten alloy.

The design and production of nozzles can maintain their structural and dimensional integrity for a planned period of time. The nozzle made of cobalt chromium tungsten alloy 6 and 12 has the longest lifespan. These two cobalt based alloys, as shown in Table 2 and Figure 3, contain approximately 30% cobalt (Co) in their composition, while the proportion of chromium (Cr) content is as high as 30%. The nozzles made of cobalt chromium tungsten alloys 6 and 12 greatly extend the product's service life and replacement cycle.

The various components of power plants affected by high temperatures, such as fuel nozzles, bushings, seals and retainers, diaphragms, protective covers, blades, and other critical components, are made of cobalt based and nickel based alloys, as some components of power plants require high temperature, wear, corrosion, and fatigue protection. Tungsten chromium cobalt alloy 6 and cobalt chromium tungsten alloy 12 have low elongation (close to 1%), high Young's modulus, dense microstructure, and high corrosion and wear resistance, providing the required physical properties. Suitable for mechanical performance of many components in power, petrochemical, and refinery industries.

Pulp and Paper Industry

Cobalt chromium tungsten alloy allows for use like tungsten chromium cobalt alloy 6. 6 b。 6K and tungsten chromium cobalt alloy 12. The Delcrome 90 solves some of the most challenging wear issues in the pulp and paper industry. Examples of these cobalt alloy components used in the pulp and paper industry are plug screw feeders, black liquor spray nozzles, palm guides, steam nozzles, feed roll points, bottom cutter brands, sleeves and bushings.

Food processing industry

Cobalt chromium tungsten alloy is mainly used in the food processing industry for components that require high wear resistance and excellent corrosion resistance. Some examples of these products are various types of knobs. Pin. In the bushes. Pistons, tableware. Cooking utensils, food processing machinery parts, and screwdriver screws.

Wood and Wood Industry

The cobalt chromium tungsten alloy tip disk serrations have better surface finish and a considerable operating time. Although the hardness of cobalt chromium tungsten alloy is lower than that of hard alloy, it has stronger wear resistance, and its toughness and toughness are sufficient to withstand impacts. The products used in conjunction with automatic and long-life saw blade dumping equipment include triangular and rectangular saw blades, spherical, triangular and trapezoidal saw blades.

Automotive Industry

The history of cobalt chromium tungsten alloys is directly related to the automotive industry. As mentioned at the beginning of this article, in 1900, Elwood P. Haynes first developed cobalt chromium tungsten alloy in a small town called Kokomo, Indiana, for the production of various key components of his invention without a carriage. He used his newly patented cobalt chromium alloy to manufacture internal combustion engine parts. Haines also discovered that some of these new cobalt alloys are more durable than the stainless steel he invented earlier. Usually cobalt chromium tungsten alloy 6. Cobalt chromium tungsten alloy 6b. Cobalt chromium tungsten alloy 12 and cobalt chromium tungsten alloy F have been used in the manufacturing of automotive parts since the early 20th century. These automotive components include pins, bushings, gaskets, shafts, wear-resistant parts, washers, camshafts, cam flanges, valves, valve stem tips, valve seats, etc., which are produced through various processes such as casting and investment casting. Adopting powder metallurgy and plasma transfer arc (PTA) technology, and adopting hot powder spraying process.

Aerospace space industry

Due to reasons such as metal to metal wear, fretting, thermal corrosion, and particle erosion, aircraft engines have various degradation problems. Due to the high temperature involved, this degradation will accelerate. Some cobalt chromium tungsten alloys, such as cobalt chromium tungsten alloy 31, cobalt chromium tungsten alloy 6, and cobalt chromium tungsten alloy 6b. Cobalt chromium tungsten alloy 3 and cobalt chromium tungsten alloy 19 are used to improve the lifespan of certain aircraft engine components. The parts produced using the aforementioned cobalt chromium tungsten alloy include flash castings, spacer sleeves, rod end bearings, and ball bearings. Static structural components such as bearing rings, fuel nozzles, cyclones, gaskets, engine blades, bearing brackets, etc. Cobalt chromium tungsten alloy 21 and cobalt chromium tungsten alloy 31 are used for casting turbine blades and in many military piston engines on aircraft.

Medical implants, instruments and devices

Cobalt chromium tungsten alloy is widely used in medical equipment due to its wear resistance and corrosion resistance. Another auxiliary use of the powder stone invented by Haines is to manufacture sharp tools for cutting tools, surgical and dental instruments. These tools must have anti-corrosion properties, be easy to clean, and be able to maintain their sharpness for a long time, which is essential for surgical procedures. Cobalt chromium tungsten alloy is used for scissors blades, needle holder blades, and other surgical tools. Cobalt chromium tungsten alloys, as well as titanium alloys to a greater extent, have significant and unique applications in industrial and biomedical fields, in some cases, as summarized below. At present, cobalt and nickel based alloys are used in the production of dental restorations, which are economically cheaper than gold and silver based alloys, but provide sufficient quality cobalt chromium tungsten alloys to produce various dental cobalt chromium tungsten alloys for the manufacture of crowns, bridges, and dentures. As mentioned above, these are the CoCr and NiCr alloys they produce for the dental industry.

In biomedical applications, metal biomaterials are used to manufacture 70-80% of implants. In the manufacturing of implants, cobalt based alloys are an improvement on the biocompatibility of titanium alloys Under specific circumstances, the ductility of Co alloy is superior to that of Ti alloy. Compared with stainless steel and titanium alloys, cobalt chromium alloy (CoCr) has the highest wear resistance and higher strength. However, the ductility and cyclic torsional strength of stainless steel are superior to those of titanium and cobalt alloys. On the other hand, titanium alloys contain nickel (Ni), which has recently been proven to be toxic to the human body, making them less biocompatible than cobalt alloys. Other applications of tungsten chromium cobalt alloy in human bone replacement and the surgical industry include single chamber tibial implants and septal tibial implants. Rotary tibial prosthesis for knee joint prosthesis and pressed ACE flat cup for hip joint prosthesis

Other application areas

Cobalt chromium tungsten alloy is used in nuclear industry. Some products made of cobalt based alloys are wires. Plate and welding rod. Cobalt chromium tungsten alloy is used to manufacture searchlight reflectors for the navy, and in a few cases, it is also used to manufacture lathe cutting tools.